Some RISC-V Post-Merge Cleanup

[Palmer Dabbelt <palmer at dabbelt dot com>]

Thanks to everyone who helped us get our port upstream.  We're still cleaning
things up on our end, but I have a few small patches to submit here.  The
MAINTAINERS patch was suggested during upstreaming and isn't very interesting.

Andrew recently went and cleaned up the floating point support in GCC and GAS
on RISC-V so now we can support the Q (128-bit floating point) extension
cleanly.  This does break stuff, but since the port has only been live since
this morning hopefully it's all OK :).

There will probably have to be a few more things like this that come up over
the next month or so as people start using the port and finding various issues
in it.  With these patches we can move our toolchain repo (which builds our GCC
and glibc ports) to use binutils-gdb/master so hopefully these sorts of issues
will get ironed out quickly.

[PATCH 1/2] Support GAS flag -mfloat-abi; remove .option
[PATCH 2/2] Andrew and I are the RISC-V maintainers